1. Field of the Invention
The present invention relates to a buffer memory device which temporarily stores input image data and outputs the stored image data to an image processing unit, and to a method for controlling the buffer memory device. Particularly, the present invention relates to a buffer memory control device which temporarily stores image data input from one of a plurality of input sources and which supplies the stored image data to one of a plurality of image processing units, and to a method for controlling the buffer memory control device, and to an image processing device and method using the buffer memory control device and control method.
2. Description of Related Art
Generally, with recording apparatuses such as laser beam printers (LBP), the image data must be continuously output to the engine at a unique image transfer speed determined according to the number of faces of the polygonal mirror used for scanning and the rotation speed thereof, while synchronizing with horizontal and vertical synchro signals. Thus, with digital copiers or the like, for example, in the event that the image transfer clock of the scanning unit is not the same as the image transfer clock used to control data transfer to the engine, a method is employed wherein two line buffer memories are used to perform conversion of the speed of the image transfer clock. Specifically, each line buffer memory is accessed at the time of memory writing of the image data output from the scanner unit, and also at the time of memory reading of the image data to be supplied to the printer engine, and the two line buffer memories are used as a speed absorption buffer to perform conversion of the speed of the image transfer clock. Also, with digital copier devices, conversion processing for converting the image data into on/off signals for the laser beam is performed at the latter tier of the aforementioned line buffer memories, as recording image processing for forming the image on paper.
Similarly, two line buffer memories are used to perform conversion of the speed of the image transfer clock with communication equipment such as facsimile apparatuses as well, since the image supplying speed of the decoder is not constant during the process of decoding the encoded image data with a decoder and recording this image. Also, since the recording resolution of the printer engine and the resolution of the image data in the image file are not the same with facsimile apparatuses, resolution conversion processing is performed at the latter tier of the aforementioned line buffer memories, as necessary. Regarding this resolution conversion processing, reference buffer memories are provided separately, to enable image processing for outline smoothing of slanted lines.
In recent years, apparatuses have been developed with complex functions, including, e.g., photocopying functions, facsimile functions, and printer functions. Such complex devices are constructed so as to output various types of image data having differing resolution and depth from a single printer engine. With complex apparatuses constructed thus, a speed absorption line buffer memory is used for transfer speed conversion for each image supplying device such as the scanner unit supplying image data to the printer engine, and there also are provided line reference buffer memories separately for each different function image process, such as resolution conversion and binarization processing.
Hence, the number of buffer memory chips used in such complex apparatus with a complex structure of photocopying functions, facsimile functions, and printer functions, increases according to the number of functions provided therein, and thus the construction of the apparatus tends to become complicated.